Boat lifts of various kinds have been developed but most are limited in one way or another because they rely on supporting underwater structures for installation and require special permits because they occupy submerged land owned by other than the riparian owner.
One structure which avoids many of these problems is disclosed in the patent to Voegeli U.S. Pat. No. 6,598,549 issued Jul. 29, 2003. In that patent the boat lift is supported from land adjacent to the water such as a bulkhead or seawall without relying on any underwater support. The Voegeli boat lift has many advantages but is limited to smaller boats because of the maximum weight of the boats that can be handled. This limitation is believed to result from the arrangement of hydraulic actuators which are disposed so that one actuator expands and the other simultaneously contracts between adjacent points on a parallelogram linkage and more widely spaced points on the land supported base structure.